Rear brake bias proportioning valve help/identification

[Chim_Pete]

I have a problem with rearward brake bias on my 1994/M pre-serp T5/box Chim. The rears are locking up before the fronts and now that winter is here it is becoming more of a problem and a potential silly accident possibility.

Can anyone tell me if the item in the photo is a bias valve? I cannot see any other inline device at the rear of the car. Apologies for the blurry photo - This is basically an oversized T-connector with the main brake line coming into the cylindrical body part and then each rear caliper hose coming out of the 'T' at the other end.

If this is it, can anyone tell me the part number or any clues? Or can I take it apart and service it? I'm guessing its just a ball a spring type arrangement a bit like a pressure relief valve? I have had two suggestions that it may be a ford or a british leyland part but nothing further...

Many thanks,

Pete.

[That Daddy]

Vauxhall use something much like what you have pictured on the mk3 cavalier rear brakes,they have coloured bands on to indicate disc brake rears or drum brake rears,certainly looks very similar(although they use one per rear brake),have you inspected the front brakes,made sure pads and calliper pistons are siding correctly and free 1st,if you have knackered 240mm front brakes then the rears will tend to overpower the fronts,as the break bias is already being pushed to favour the rears(bigger brakes)

Edited by That Daddy on Thursday 6th December 14:16

[AntonyJ]

If its the same as mine (92 griff) then its a Sierra deceleration valve and is mentioned in the Haynes sierra manual.
Havent actually tried to get one yet, but pretty sure thats what it is......

[spend]

You sure Ant, mine doesn't look quite like that, its squater and looks more like a solid one-piece body. I just put down to early vs later?

Dave

[peteA]

that is the brake bias unit - mine was leaking and I had to order another one - got it from a breakers (douglas valley)

[AntonyJ]

spend said:

You sure Ant, mine doesn't look quite like that, its squater and looks more like a solid one-piece body. I just put down to early vs later?

Dave

Not 100% Dave, just know mine that is on the garage floor matches the pic in the sierra haynes manual.

[Chim_Pete]

peteA said:

that is the brake bias unit

Thanks for the confirmation. Now, does anyone have any further idea as to the part origin of my type? Also can it be serviced or will i definately need a new one?

Thanks for all the replies.

Pete.

[That Daddy]

They cant be serviced(well not by us anyways)their probably shared by various car manafacturers models,probably made by someone like Ate,Lockheed,Tieves etc, anyway the problem is they can look the same on the outside but be valved differently inside,as said earlier when i have changed these on vauxhalls in the past(leaking from the body join) the guys at the dealer always needed to know the colour of the plastic ring on it,green,blue,yellow etc,that does not appear to be like your one though(no ring in picture showing)

[GreenV8S]

If you've got a bit too much rear bias, that probably shows the bias valve is working properly. If you've got waay to much at the rear, the valve is probably ucked. (No offense to the person who designed the brakes, but who TF thought it was a good idea to put the brake balance so far to the rear as standard?)

[Chim_Pete]

GreenV8S said:

If you've got a bit too much rear bias, that probably shows the bias valve is working properly. If you've got waay to much at the rear, the valve is probably ucked. (No offense to the person who designed the brakes, but who TF thought it was a good idea to put the brake balance so far to the rear as standard?)

Are you saying that "they're all like that sir"? I don't remember mine being like this in the past, and haven't changed any part of the brake system that would cause a change. On wet days like today I can brake progressively hard and simply lock the rear wheels as if I had applied the handbrake. It's nearly caught me out a couple of times when braking hard and suddenly whilst turning and ending up sliding sideways down the road! It won't take many more of those experiences before I end up stacking the car, and for a stupid reason.

Maybe I should replace the bias unit with an adjustable willwood/ap unit. Have seen these for ~£40. Has anyone done this?

Cheers.

Edited by Chim_Pete on Thursday 6th December 21:15

[sparkythecat]

Chim_Pete said:

It's nearly caught me out a couple of times when braking hard and suddenly whilst turning and ending up sliding sideways down the road! It won't take many more of those experiences before I end up stacking the car, and for a stupid reason.

Pete, this isn't meant as any sort of put down, but except in a dire emergency, you really shouldn't be doing that in a TVR, particularly in adverse weather conditions. Regardless of whether or not the brake balance is as it should be,
that's still a recipe for disaster.

[GreenV8S]

Chim_Pete said:

Are you saying that "they're all like that sir"?

Well there's no such thing as a standard where TVRs are concerned, but there seems to be a consistent trend for TVRs of the S/Chim/Griff era to have a lot more rear braking than I personally think is desirable. This results in cars that tend to be tail happy under braking. The driver can mask or exaggerate these characteristics depending how they apply the brakes and what engine/clutch braking they apply, but this underlying characteristic is IMO making the cars far more tricky under braking than they need to be.

[Chim_Pete]

sparkythecat said:

Pete, this isn't meant as any sort of put down, but except in a dire emergency, you really shouldn't be doing that in a TVR, particularly in adverse weather conditions. Regardless of whether or not the brake balance is as it should be,
that's still a recipe for disaster.

Yep, its not desirable to brake whilst cornering in any car, but when theres a hazard on the road sometimes you don't have a choice-like when I came round a sharpish blind corner a few months ago, 60mph limit, and found a stationary van just after the exit of the corner!! yikes!

[Chim_Pete]

Just to update this thread...

At the time of previously writing my rear wheels were shod with 16" B'stone S02's (not Pole Positions) on standard wheels.

I replaced these a while a go with Falken FK452's. This has improved the brake balance considerably. I got loads of mileage out of the S02's (>12k miles since I bought the car and they weren't new then!), but think they are a bit too hard and when they were nearly worn out the grip definately diminished. Definately not good for December/January weather!

So, new rear tyres were the answer to my brake balance woes. Its not ideal, but a lot better than it was....

Cheers,

Pete.